As we are in preview version there are couple of tools which are there to help developers to quickly complete their job. The new implementations in SP 2013 like Apps for office and Apps for SharePoint 2013 etc. are also a WSP package. They are also having the same structure as the general WSP packages we developed for 2010 environment.
‘Napa’ tools for Office 365 Development:
If you are having your SharePoint 2013 environment on the cloud then your life is so easy to develop the Apps. “Napa” Office 365 Development Tools provides you a great way to build apps for Office or SharePoint directly out of a browser windows.
You might be thinking now, are there need of Visual Studio or any other tools needs to be installed on the server? No, its not required. All you need is just Office 365 account and the latest browsers. You might need Visual Studio in case if you want to debug your app or writing any complex code etc..
You can find more details about it on MSDN here.
SharePoint Developer Tools for Visual Studio 2012:
To develop SharePoint solutions in Visual Studio 2012 we must need these SharePoint developer tools. You can install them from here. Once you installed, you will see the new templates in Visual Studio for 2013 as shown.
SharePoint Designer 2013 and Visio 2013:
The SharePoint Designer is improved in many aspects. There are powerful implementations including ability to create .net 4.x workflows, new visual designer, loops [you can implement loop through items, wow.], calling web services, start workflow actions, packaging of workflows, dictionary [array] type variables etc.. So, IT guys can do much more than what they did compared to earlier versions without writing single line of code. It can address solutions to so many issues we had in earlier implementations with new SharePoint designer.
Visio 2013 also looks really cool and you can build powerful workflows and publish them with ease of development. Visio 2013 diagram now can connect to external data sources to use external data in the diagrams/workflows.